Metal working lubricant

ABSTRACT

Aqueous emulsions of fluid organopolysiloxanes containing at least 25 mol percent of higher alkyl substituents, such as a 50/50 copolymer of C8H17SiO3/2 and (CH3)2SiO units, are used as lubricants in metal working processes, such as cutting aluminum.

United States Patent 1 1 1111 3,756,052 Quaal et a1. Sept. 4, 1973 [54] METAL WORKING LUBRICANT 3,429,909 2/1969 Schuster 252/493 X 3,632,619 1/1972 Groenhof 252/496 [75] Inventors: Gem'ge Quaal; Eugene 3,408,843 11/1968 Treat 252/495 x Groenhot', both of Midland; Robert J. Kelly, Bridgeport, all of Mich. [73] Assignee: Dow-Corning Corporation, Midland, Primary Mich. Assistant ExammerW. Cannon Attorney-Robert F. Fleming, Jr. et a1. [22] Filed: Dec. 27, 1971 [21] Appl. N0.: 212,727

' [57] ABSTRACT [52] US. Cl. 72/42, 252/495 [51] Int. Cl ClOm 1/06 Aqueou emulsions of fluid organopolysiloxanes con- 1 Field of Search taining at least 25 mol percent of higher alkyl substitu- 72/42 ents, such as a 50/50 copolymer of C,,H ,SiO and (Cl-l SiO units, are used as lubricants in metal work- [56] Relerences Cited ing processes, such as cutting aluminum.

UNlTED STATES PATENTS 3,457,173 7/I969 Pater 252/4911 7 Claims, No Drawings METAL WORKING LUBRICANT This invention relates to a water-based metal working lubricant. In one aspect, the invention relates to lubrieating metals during the process of forming such metals.

Metal working industries utilize a variety of lubricants. Water-based cutting fluids exhibit cooling characteristics when used in processing metals but lack lubricity. Oil-based metal working fluids are relatively costly and possess poor heat transfer properties. Another class of cutting fluids, soluble oils in emulsified form, are used to obtain lubricity while retaining the coolant function of aqueous systems.

The present invention is based on the discovery that certain organosiloxane polymers in an aqueous emulsion provide excellent lubrication and cooling during metal forming operations, such as grinding and cutting. More particularly, the invention provides a method of forming a solid metal article comprising, prior to or during forming, lubricating the surface of said metal with an aqueous emulsion containing at least 0.5 weight percent of an organopolysiloxane fluid of the formula [R SiO, in which R is selected from the group consisting of monovalent hydrocarbon radicals containing from 1 to 18 inclusive carbon atoms and monovalent halohydrocarbon radicals containing from 1 to 18 inclusive carbon atoms; R being free of aliphatic unsaturation; at least 30 percent of the R substituents being alkyl radicals containing from 8 to 18 inclusive carbon atoms; n has a value of from 1 to 3 inclusive, m is so selected as to yield a polymer having a viscosity of from about to about 1,500 cs. when measured at C.

In the above-defined organopolysiloxane, the R substituents can be any monovalent hydrocarbon radical free of aliphatic unsaturation and containing from 1 to 18 inclusive carbon atoms. Exemplary of such monovalent hydrocarbon radicals are alkyl radicals, for examle, methyl, ethyl, isopropyl, octadecyl or myricyl; cycloaliphatic hydrocarbon radicals such as cyclopentyl, cyclohexyl or methylcyclohexyl; aryl hydrocarbon radicals such as phenyl, xenyl, tolyl, xylyl, naphthyl or anthracyl and aralkyl hydrocarbon radicals such as benzyl, Z-phenylethyl, or 2-phenylpropyl.

Also within the scope of R are halongenated monovalent hydrocarbon radicals free of aliphatic unsaturation and containing from 1 to 18 inclusive carbon atoms, such as haloalkyl radicals, for example, any halogentated monovalent hydrocarbon radical free of aliphatic unsaturation such as haloalkyl radicals such as chloromethyl, 3-chloropropyl, bromooctadecyl, 3,3,3- trichloropropyl, chloroisopropyl or 2-(perfluoroalkyl- )ethyl radicals in which the perfluoroalkyl radical is trifluoromethyl, perfluoroethyl, perfluoroisobutyl or perfluorooctadecyl; halocycloalkyl radicals such as bromocyclohexyl, chlorocyclopentyl or fluorocyclohexyl; haloaryl radicals such as 2,4-dichlorophenyl, dibromoxenyl, alpha,alpha,alpha-trifluorotolyl, iodonaphthyl and tetrachlorophenyl and haloaralkyl radicals such as 2-(chlorophenyl)-ethyl, p-chlorobenzyl or 2-(bromophenyl)propyl.

In order to provide lubricity in the metal working emulsion, the organopolysiioxane must have at least 25 mo] percent of the R substituents selected from the group consisting of alkyl radicals containing from 8 to 18 inclusive carbon atoms. Exemplary of such R substituents are octyi, 2-ethylhexyl, nonyl, dodecyl, heptadecyl and octadecyl radicals. Siloxanes having alkyl substituents with less than 8 carbon atoms do not exhibit significant lubricity in the aqueous system. Emulsion containing a substantial amount of siloxanes having greater than 18 carbon atoms in the substituents do not have the stability necessary for use in the forming of metals.

The defined organosiloxanes are relatively low molecular weight polymers having viscosity in the range of from about 20 to about 1,500 cs. (centistokes) as measured at 25C. To provide ease in forming emulsions, it is preferred that the organopolysiloxane have a viscosity of from 20 to 500 csJThe polymeric u'nits present in the organopolysiloxane include RSiO R SiO and R SiO Both homopolymers and copolymers can be utilized in the practice of the invention. The polymers can be cyclic, such as [CH (C H, )SiO] or linear, Such as Si(CI-I Preferred polymers utilized in the practice of the invention are R"(R) SiOSi(R) R" and (R'R"Si0),, in which R is an alkyl radical containing from 1 to 6 inclusive carbon atoms; R" is an alkyl radical containing from 8 to 14 inclusive carbon atoms. Of course, mixtures of the above-described polymers can be used if desired.

The organopolysiloxanes are dispersed in water to form an emulsion. Conventional emulsifying agents, such as sorbitan monolaurate, can be used in the preparation of the emulsion. When used as a metal working fluid, the emulsion should contain at least 0.5 weight percent of the organopolysiloxane to obtain lubrication, although, in some cutting operations an even lower concentration can be used. For most metal forming processes it is preferred that the concentration of siloxane be one weight percent or more. Concentrations of 20 percent or more of siloxane in the emulsion do not provide enhanced lubrication, except in the machining of certain alloys.

In addition, to emulsifying agents the metal working fluid can contain conventional additives such as corrosion inhibitors, antioxidants, bactericides, freezing point depressants, metal deactivators and the like. The additives are present in relatively small amounts, generally not exceeding 10 weight percent of the emulsion.

The emulsion can be applied to the solid metal bydipping, rushing, spraying, coninuous flooding by recycling or other conventional techniques. In most metal forming operations, such as sawing, grinding and milling, the fluid is applied during the forming, but in some forming processes, such as drawing and extruding, the emulsion can be applied prior to forming. Metal forming processes benefiting from the use of the described lubricant/coolant include grinding, turning, milling, boring, tapping, sawing, slotting, drawing, extruding and the like. The list of metals commonly subjcted to such forming processes is extensive but includes aluminum, copper, brass, cast iron, soft steel and nickel alloys.

The following examples are illustrative and not to be construed as limiting of the invention delineated in the claims.

EXAMPLE 1 An organopolysiloxane of the formula C I-I (CH SiOSi(Cl-I C, I-I having a viscoisty of 58 cs. at 25C. was mixed in water solution of additives in an amount sufficient to provide an emulsion containing 24 weight percent of the alkyldimethylsiloxane, 7.1 weight percent of sorbitan monolaurate (emulsifier), 0.3 weight percent sodium nitrate (corrosion inhibitor), 0.3 weight percent of a commercially available bactericide and 68.3 weight percent water. The emulsion was prepared by homogenization. This emulsion was diluted with water to obtain a cutting fluid containing weight percent organopolysiloxane and the cutting fluid was evaluated by means of the Soconoy- Mobil Tapping Method, as described in Lubrication Engineering, Vol. l2, No. 5 (May, 1956), pp. l99203. Holes in aluminum test bars were tapped using precision ground steel taps while the coolant/lubricant was flowed over the workpiece. The average torque for the described metal working fluid was 1.0 in.-lb. This torque, developed during the internal threading operation, must be compared to the average value of l.8in.- lb. obtained by the same test using an equivalent fluid containing trimethylsilyl terminated dimethylpolysiloxane (50 cs.); 1.9 in.-lb. obtained by use of trimethylsilyl terminated trifluoropropylmethylpolysiloxane (130 cs.); and L7 in.-lb.- obtained by the use of an emulsion containing 5 weight percent of a phenylmethylpolysiloxane. Thus, the data demonstrate the superiority of higher alkyl-substituted siloxanes over metal working fluids based on other types of organopolysiloxanes.

EXAMPLE 2 A mixture of siloxanes of the formula [C H (CH )SiO],,, in which m was equal to 3, 4, 5 and 6 was added to water to form an emulsion containing 35 weight percent of the mixed cyclic polymers, 3.5 weight percent of sorbitan monolaurate, 0.1 weight percent sodium nitrate, and 0.1 weight percent bactericide. The emulsion was diluted to provide a cutting fluid containing 5 weight percent of the siloxanes. Utilizing this fluid in the previously-described tapping test resulted in a torque of 0.65 in.-lb. Further dilution to about the 2.5 weight percent level resulted in a torque of 1.0 in.-lb. Utilizing an emulsion of the same components containing 9 weight percent of the siloxane mixture gave a torque value of 0.25 in.-lb. Thus, the fabricator can bary vary siloxane content of the metal working emulsion to optimum lubrication.

EXAM PLE 3 An organopolysiloxane consisting of equimolar parts of C H SiO units and (CH SiO units and having a viscosity of 33 cs. at C. was homogenized in water to form a 5 weight percent emulsion. When utilized as a coolant/lubricant in the described tapping test, this emulsion resulted in a tapping torque of 0.8 in.-lb. Further dilution of the emulsion to the 1 weight percent siloxane level raised the tapping torque to 1.1 in.-lb.

EXAMPLE 4 A copolymeric siloxane of the formula [CiliitfHCHflCHQSIO] Susan. CH: 0.:

having a viscosity of 1,200 cs. at 25C. was mixed with water to form a 5 weight percent emulsion which when utilized as the lubricant in the tapping test resulted in a torque of 1.0 in.-lb.

Reasonable modification and variation are within the scope of the invention which is directed to a method of forming metals.

That which is claimed is:

1. in the method of forming a solid metal article the improvement which comprises, prior to or during forming, lubricating the surface of said metal with an aqueous emulsion containing at least 0.5 weight percent of an organopolysiloxane fluid of the formula [R,,SiO in which R is selected from the group consisting of monovalent hydrocarbon radicals containing from 1 to 18 inclusive carbon atoms and monovalent halohydrocarbon radicals containing from 1 to 18 inclusive carbon atoms; R being free of aliphatic unsaturation; at least 30 percent of the R substituents being alkyl radicals containing from 8 to 18 inclusive carbon atoms; n has a value of from 1 to 3 inclusive, m is so selected as to yield a polymer having a viscosity of from about 20 to about 1,500 cs. when measured at 2. The method of claim 1 wherein the metal is aluminum.

3. The method of claim 1 wherein the forming includes cutting.

4. The method of claim 1 wherein m is so selected as to yield a polymer having a viscosity of from 20 to 500 7. The method of claim 1 wherein the organopolysiloxane is of the formula m." 51. C]1H15Sl0 -Si C H Ha Ha U.S. PATENT oEEICE UNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,75 5 I Dated: September A, 19'

It is certified that errors appear in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

-- LR SiO 1 Signed and sealed this 1mm day of May 197E. I

(SEAL) Attest:

EDWARD I IJFLETGIZEILJR. C. MARSHALL DANH Attesting Officer C Commissioner of Patents 

2. The method of claim 1 wherein the metal is aluminum.
 3. The method of claim 1 wherein the forming includes cutting.
 4. The method of claim 1 wherein m is so selected as to yield a polymer having a viscosity of from 20 to 500 cs. when measured at 25*C.
 5. The method of claim 1 wherein the organosiloxane is of the formula (R''R''''SiO)m in which R'' is an alkyl radical containing from 1 to 6 inclusive carbon atoms; R'''' is an alkyl radical containing from 8 to 14 inclusive carbon atoms and m has a value of 3 to 6 inclusive.
 6. The method of claim 4 wherein the organopolysiloxane is of the formula (CH3(C14H29)SiO)m
 7. The method of claim 1 wherein the organopolysiloxane is of the formula 